WHILE the majority, about 75 to 80 per cent of Zika infections, are so mild that people do not realise they are infected, recent discoveries suggest that in a small minority of cases people may suffer consequences that are just being revealed.

The finding of high concentrations of the Zika virus within the cerebro-spinal fluid (liquid around the brain and spinal cord), blood, and urine of a 15-year-old girl admitted to hospital with partial paralysis, limb weakness and intense pain in the eastern Caribbean island of Guadeloupe, suggests that the Zika virus may well have been the cause for her symptoms. The Zika virus was also found in the fluid surrounding the brain and spinal cord of an 81-year-old man hospitalised in Paris, France, with partial paralysis, fever and semi-consciousness.

ACUTE MYELITIS

Acute myelitis is a neurological condition in which the spinal cord becomes inflamed.

The inflammation may damage nerve fibres, causing them to lose their myelin protective coating, thereby leading to decreased electrical conductivity within the central nervous system. This can cause weakness and paralysis generally across the body. As both afferent nerves (that carry sensory impulses up to the brain) and efferent nerves (that carry motor commands from the brain down to the limbs) may be affected, feelings of ‘pins and needles’, pain, as well as loss of movement and motor skills may occur.

If the autonomic nervous system in the spinal cord is also affected, there may be a loss of both bladder function and bowel control, as well as episodes of high blood pressure. Severe cases of myelitis may need specialised care by a neurologist in hospital, with treatment often involving high doses of steroids, given to suppress the inflammatory process and lessen the swelling of the spinal cord.

Depending on the cause of the myelitis (eg viruses, bacteria, fungal, autoimmune) and the patient’s response, recovery may begin to occur between two weeks and three months, and may take up to two years for full recovery. However, some people never achieve complete recovery.

OTHER ZIKA-ASSOCIATED ILLNESSES

Over the last three weeks, two separate laboratories have found the first evidence of a biological link between Zika and the microcephaly (small head size) seen in some newborns of mothers who were infected with Zika. The laboratory testing found that Zika targeted important cells involved in brain development and then disabled or destroyed them.

A separate study also offered evidence that Zika may cause Guillain-Barre syndrome in adults, a usually rare condition in which the body’s immune system attacks the part of the nervous system that controls the muscles of the body.

Until recently, Zika was thought to be a mild virus that caused only benign infections in humans. However, there is now increasing evidence that Zika may be neurotropic, that is, being attracted to and attacking the nervous system.

There has also been more than a handful of reported cases of Zika being transmitted by sexual intercourse. The Zika virus was first found to be present in the semen of a 44-year-old man from Tahiti, who was exposed during the outbreak of Zika in French Polynesia in 2013. French scientists, helping to investigate, found high levels of the virus present in the semen samples taken from the patient, even after the virus had disappeared from his blood. However, it was unclear how long the virus had persisted in the semen as the patient had had two bouts of fever, either of which could have been caused by Zika infection — one shortly before he was tested and another about two months earlier.

THE MESSAGE

More research is therefore needed on the Zika virus which, hitherto, was unable to attract any research money as Zika, until recently, was considered an obscure virus. Problematically, Zika is more difficult to study as normally, studies of viruses are first done in rats, mice, and other laboratory animals, but Zika does not infect these animals.

It infects monkeys, but doing such studies is more difficult, expensive, as well as more controversial. Establishing a monkey research colony within a commercial laboratory or university for Zika virus studies would invoke many ethical and socio-political issues.

On the other hand, we now know that Zika may have significant effects beyond those on pregnant women, and that the effects are not always benign.

Whilst only Brazil and French Polynesia have reported an increase in cases of microcephaly associated with the Zika outbreak in those countries, eight of the 41 countries or territories that have reported Zika infections to the World Health Organization have informed of increased numbers of Guillain-Barré cases. Consequently, as there is currently no vaccine or effective treatment for Zika, we must be aware of all these issues and make aggressive and sustained attempts to eliminate the Aedes aegypti mosquito from our environment.

Derrick Aarons MD, PhD is a consultant bioethicist/family physician, a specialist in ethical issues in medicine, the life sciences and research, and is the ethicist at the Caribbean Public Health Agency (CARPHA). (The views expressed here are not written on behalf of CARPHA)